[RFC PATCH 2/2] arm: pcibios: move to generic PCI domains

[Phil Edworthy]

Hi Bjorn,

On 31 October 2014 16:37, Bjorn wrote:
> On Fri, Oct 31, 2014 at 7:43 AM, Phil Edworthy
> <phil.edworthy at renesas.com> wrote:
> > Hi Lorenzo,
> >
> > On 30 October 2014 11:45, Lorenzo wrote:
> >> Most if not all ARM PCI host controller device drivers either ignore the
> >> domain field in the pci_sys_data structure or just increment it every
> >> time a host controller is probed, using it as a domain counter.
> >>
> >> Therefore, instead of relying on pci_sys_data to stash the domain number
> >> in a standard location, ARM pcibios code can be moved to the newly
> >> introduced generic PCI domains code, implemented in commits:
> >>
> >> commit 41e5c0f81d3e676d671d96a0a1fafb27abfbd9
> >> ("of/pci: Add pci_get_new_domain_nr() and of_get_pci_domain_nr()")
> >>
> >> commit 670ba0c8883b576d0aec28bd7a838358a4be1
> >> ("PCI: Add generic domain handling")
> >>
> >> In order to assign a domain number dynamically, the ARM pcibios defines
> >> the function, called by core PCI code:
> >>
> >> void pci_bus_assign_domain_nr(...)
> >>
> >> that relies on a DT property to define the domain number or falls back to
> >> a counter; its usage replaces the current domain assignment code in PCI
> >> host controllers present in the kernel.
> >>
> >> Cc: Arnd Bergmann <arnd at arndb.de>
> >> Cc: Phil Edworthy <phil.edworthy at renesas.com>
> >> Cc: Jason Gunthorpe <jgunthorpe at obsidianresearch.com>
> >> Cc: Jingoo Han <jg1.han at samsung.com>
> >> Cc: Bjorn Helgaas <bhelgaas at google.com>
> >> Cc: Russell King <linux at arm.linux.org.uk>
> >> Cc: Mohit Kumar <mohit.kumar at st.com>
> >> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> >
> > This patch fixes a current problem with R-Car devices where there is an
> > internal PCI bridge and an external PCIe bridge on the devices. Both drivers
> > work independently but need to be on different domains. Just needed to
> enable
> > PCI_DOMAINS along with this.
> > I've done basic testing that the internal PCI and external PCIe work at the
> > same time.
> 
> Hi Phil,
> 
> Thanks for testing this.  Can you give me some more guidance on where
> you'd like to see this merged?  Until your comment about this fixing a
> current problem on R-Car, I probably would have considered this to be
> a cleanup and enhancement and hence material for v3.19.  But if R-Car
> is actually broken and this fixes it, maybe this should go in for
> v3.18 instead.
I don’t think its urgent as most of our customers use LTSI kernels, e.g. v3.10.
Renesas typically provide out-of-tree BSPs with upstream code back ported, along
with other patches. Simon Horman (Renesas maintainer, cc'd) generally handles
the back ports, so I'll defer to his opinion.

> If it is currently broken, is there a point where it broke?  I assume
> it used to work at one time.  If there's a commit that broke it, it
> would be nice to reference that in the changelog and explain exactly
> what was broken and how this fixes it.
Both the internal PCI and external PCIe drivers work on their own, but have
never worked at the same time. I think it was just unfortunate timing when I
added the PCIe driver. At that time, the internal PCI driver didn’t have the
relevant DT nodes for the board I was using so I didn't see any conflicts.

Thanks
Phil